The present invention relates to vehicle brakes, and in particular, to a disc brake caliper integrating a parking brake therein.
The present invention relates to vehicle brakes, and in particular, to a disc brake caliper integrating a parking brake therein.
A disc brake operates on the principal of hydraulically actuating a piston in a caliper to force opposing brake pads against parallel faces of a rotor attached to the rotating wheel. Such a configuration is generally shown in FIG. 1. It is also known in the art to incorporate a parking brake within the caliper, and such a prior art parking brake 90 is shown in FIG. 2. The prior art parking brake and caliper combination comprises a caliper housing 91 having an internal cavity 100 within which piston 92 is acted upon by brake fluid to translate piston 92 with respect to caliper housing 91. A threaded pin extends through caliper housing 91 and into cavity 100 and piston 92. The shaft of threaded pin 93 incorporates high-lead external threads 94 upon which is received a threaded sleeve 95 having mating high-lead internal threads. A roller clutch 96 is positioned around the exterior of threaded sleeve 95 such that when pin 93 is rotated by lever 99, the high-lead threads cause sleeve 95 to rotate with pin 93 until roller clutch engages an outer wall of sleeve 95 and an inner wall of piston 92 to rotationally lock in place sleeve 95 with respect to piston 92. Once sleeve 95 is rotationally locked in place with respect to piston 92, the high-lead threads 94 of pin 93 drive sleeve 95 and piston 96 to the left thereby forcing opposing brake pads against the brake rotor to prevent rotation of the wheel and thereby providing the parking brake function. Thrust washer 97 and retainer 98 maintain sleeve 95 in a relatively constant axial relationship with respect to piston 92. As the brake pads wear, piston 92 self adjusts to the left and thrust washer 97 correspondingly forces sleeve 95 to the left along the high-lead threads 94 of pin 93 when roller clutch 96 is disengaged.
Incorporation of this configuration for a parking brake in a disc brake caliper poses some problems such as the threads becoming worn or jammed with respect to each other. These problems can potentially result in the failure of the parking brake to engage or the failure of the parking brake to disengage. Additionally, the use of high-lead threads to induce the compression of the opposing brake pads upon the brake rotor is relatively inefficient thereby requiring a significant torquing force to be applied to pin 93 to affect the required force of the brake pads against the brake rotor. Thus, there is a need for a disc brake caliper incorporating an integrated parking brake of greater reliability that further requires a lower torquing force applied to the parking brake to affect the braking function.
One aspect of the present invention is a disc brake caliper with an integral parking brake. The caliper includes a caliper housing defining a cavity therein and a piston axially translatable within the cavity and having an internal bearing surface. At least one brake pad is affixed to either the piston or the caliper housing. A parking brake mechanism is mounted within the cavity and is interposed between a portion of the housing and the piston. The parking brake mechanism includes a thrust pin substantially axially aligned with the piston and rotatable within the housing. A first radial clutch is engageable with the thrust pin, and a second axial clutch is operable upon the piston. Rotation of the thrust pin in a first direction causes engagement of the first radial clutch and of the second axial clutch causing axial displacement of the piston. Rotation of the thrust pin in an opposite direction causes disengagement of the first and said second clutches.
Another aspect of the current invention is a parking brake mechanism for a disc brake caliper of the type having a caliper housing defining a piston cavity. The parking brake mechanism includes a piston defining a central cavity at one end thereof and further including a bearing surface. A thrust pin having a cylindrical shank at one end and a thrust shoulder at an opposite end has at least a portion of the shank received in the piston cavity. A first radial clutch extends about the thrust pin shank and is interposed between the piston and the thrust shoulder. A second axial clutch is operable by the radial clutch and is proximate to the piston-bearing surface.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.